Lightly Branched Higher Olefin Oligomerization with Surface Modified Zeolite Catalyst

ABSTRACT

A substantially surface-deactivated catalyst composition that is stable at least to 300° C. The catalyst includes a zeolite catalyst (e.g., ZSM-22, ZSM-23, or ZSM-57) having active internal Brönsted acid sites and a surface-deactivating amount of a rare earth or yttrium oxide (e.g., chosen from lanthanum oxide or lanthanides oxide). This to catalyst is preferably used in a process for producing a higher olefin by oligomerizing a light olefin, wherein the process includes contacting a light olefin under oligomerization conditions with the substantially surface-deactivated catalyst composition.

FIELD

The present disclosure generally relates to catalyst compositions forthe production of olefin derivatives, for example, higher olefins,wherein the catalyst composition is a 10-ring zeolite whose surfaceacidity has been modified by incipient wetness treatment with an yttriumor rare earth oxide. The present disclosure is useful in higher olefinproduction processes using the compositions. This disclosure is usefulin processes for higher olefin production with reduced branching of thehigher olefins. The catalyst compositions typically comprise 10-ringzeolites with alumina binder and high temperature stable modifiers thatreduce the surface acidity.

BACKGROUND

Solid acid catalysts have been used commercially for oligomerization ofolefinic feedstock. In an oligomerization process monomers are convertedto a finite degree of polymerization. In processes using olefinicfeedstock, light olefins (C₃ ⁼ to C₅ ⁼) are converted typically intobranched olefins in the C₆-C₁₅ range using solid phosphoric acidcatalyst (sPa). The sPa process was developed by UOP in the 1930's. Thisprocess has a number of drawbacks: (1) low catalyst life due to pelletdisintegration causing reactor pressure drop; (2) environmental wastehandling problems; and (3) operational and quality constraints limitflexible feedstock. Previously it has been found that acidic zeoliteswith 10-ring pores, such as ZSM-22, ZSM-23, and ZSM-57, are goodalternative catalysts for olefin oligomerization, wherein branchedhigher olefins are produced from light olefins. These branched higherolefins are further derivatized to branched (OXO) alcohols which in turnare esterified to produce esters that are used as plasticizers.Additionally, these branched higher olefins are hydrogenated to producedesired hydrocarbon solvents. Further, these lightly branched higherolefins are useful in alkylation of benzene or phenol to producesulfonate detergent precursors. Zeolite technology offers severaladvantages compared with the older sPa technology including ease ofhandling, higher catalytic activity, improved product selectivity, andfacile catalyst regeneration capability.

U.S. Pat. No. 5,026,933 (Blain et al.) discloses the use of 10-memberring zeolites for higher olefin production. That is, heavy distillateand lubricant range hydrocarbons can be synthesized over ZSM-5 typecatalysts at elevated temperature and pressure to provide a producthaving substantially linear molecular conformations due to theellipsoidal shape of these catalysts. Conversion of olefins to gasolineand/or distillate products is disclosed in U.S. Pat. Nos. 3,960,978 and4,021,502 (Givens, Plank and Rosinski) wherein gaseous olefins in therange of ethylene to pentene, either alone or in admixture withparaffins are converted into an olefinic gasoline blending to stock bycontacting the olefins with a catalyst bed made up of a ZSM-5 typezeolite. Such a technique has been developed by Garwood, et al, asdisclosed in European Patent Application No. 83301391.5, published 29Sep. 1983. In U.S. Pat. Nos. 4,150,062; 4,211,640; 4,227,992; and4,547,613 Garwood, et al. disclose operating conditions for a processfor selective conversion of C₃+ olefins to mainly aliphatichydrocarbons. In the process for catalytic conversion of olefins toheavier hydrocarbons by catalytic oligomerization using a medium poreshape selective acid crystalline zeolite, process conditions can bevaried to favor the formation of hydrocarbons of varying molecularweight. At moderate temperature and relatively high pressure, theconversion conditions favor C₁₀+ aliphatic product. Lower olefinicfeedstocks containing C₂-C₈ alkenes may be converted; however, thedistillate mode conditions do not convert a major fraction of ethylene.A typical reactive feedstock consists essentially of C₃-C₆ mono-olefins,with varying amounts of non-reactive paraffins and the like beingacceptable components. One conventional process for producingsubstantially linear hydrocarbons by oligomerizing a lower olefin atelevated temperature and pressure comprises contacting the lower olefinunder polymerization conditions with siliceous acidic ZSM-23 zeolitehaving Bronsted acid activity; wherein the zeolite has acidic poreactivity and wherein the zeolite surface is rendered substantiallyinactive for acidic reactions, the zeolite surface being neutralized bya bulky trialkyl pyridine compound having an effective cross-sectionlarger than the zeolite pore.

Although higher olefins produced from zeolite-based catalysts have lowerbranching than those made with sPa, it is highly desirable to furtherreduce branching of higher olefin product streams. It is known thatcollidine (2,4,6-trimethylpyridine) is an effective agent to deactivatesurface acid sites of 10-ring zeolites, thus improving catalystselectivity toward production of less-branched higher olefin productsfrom olefin containing feedstocks. However, a drawback of collidine isits tendency to desorb from the surface under reaction olefinoligomerization conditions. Desorption is especially troublesome if theoligomerization reaction temperature is higher than 240° C. For olefinoligomerization process, typical commercial end of cycle temperature isabout 250° C.

Collidine co-boils with 1-decene and desorbed collidine couldcontaminate higher olefin products and derivatives, such as branchedalcohols produced in a down-stream OXO process. In order to maintain aconstant level of collidine on zeolite, a continuous co-feeding ofcollidine with feed olefin is required. Another drawback oforganic-based surface treatment is collindines inability to surviveair-regeneration of the spent catalyst. That is, air regeneration burnsoff the organics, such as collidine. The inorganic species (such aszeolites, yttria and La-oxide) remain intact.

Accordingly, the composition of surface modified 10-ring zeolitecatalysts requires the control of the surface acidity of the catalyst toenable a product higher olefin containing stream with low branchinglevels per molecule. For example, one such technique is to treat the10-ring zeolite catalyst with an organic base such as collidine.However, because the collidine modified zeolite catalyst is notthermally stable at end of run temperatures, there is leaching ofcollidine and potentially contamination of the higher olefin containingproduct stream. Moreover, the high temperature air regeneration ofcollidine modified catalyst leads to decomposition of the collidine.Therefore, collidine treatment has to be repeated after each airregeneration before the catalyst can be used for higher olefinproduction.

There is a continuing need for improvement in the catalyst for olefinoligomerization reactions of the type described above. In particularthere is a need for effective surface modified zeolite catalysts suchthat they are stable to end of run olefin oligomerization temperature,do not leach an organic base into the higher olefin product stream andare air regenerable.

The present disclosure provides a novel alternate catalyst system forolefin oligomerization to lightly branched higher olefins, stable to endof oligomerization reaction temperatures, stable to air regeneration,and does not leach organic base to contaminate the higher olefin productstream.

SUMMARY

A substantially surface-deactivated catalyst composition comprising azeolite catalyst having active internal Brönsted acid sites andcontaining a surface-deactivating amount of a rare earth or yttriumoxide. Preferably, the catalyst composition is stable at least to about300° C. (i.e., air regeneration temperature is generally between about400 to about 540° C.). The catalyst composition preferably exhibits asubstantially deactivated surface acidity.

A process for producing a higher olefin by oligomerizing a lower olefin,the process comprising: contacting the lower olefin underoligomerization conditions with a substantially surface-deactivatedcatalyst composition comprising a zeolite catalyst having activeinternal Brönsted acid sites and substantially inactive surface acidsites achieved by the presence of a rare earth or yttrium oxide on thesurface.

A method of making a higher olefin from a lower olefin containingstream, the method comprising: contacting the olefin containing streamwith a surface-deactivated catalyst composition comprising a zeolitecatalyst having active internal Brönsted acid sites and substantiallyinactive surface acid sites achieved by the presence of a rare earth oryttrium oxide on the surface, thereby producing a higher olefin streamand a lighter olefin or vent stream; separating the lighter olefin orvent stream from the higher olefin stream; and contacting a portion ofthe separated lighter or vent stream with the surface-deactivatedcatalyst composition. The method further comprising contacting at leasta portion of the higher olefin stream with a catalyst forhydroformylation.

These and other features and attributes of the disclosed compositionsand oligomerization processes of the present disclosure and theiradvantageous applications and/or uses will be apparent from the detaileddescription which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the performance of Yttria-containing ZSM-22 according tothe present disclosure.

DETAILED DESCRIPTION

A method for the preparation of olefin oligomerization catalystscomprising a ten-ring zeolite with its surface acid sites deactivatedwith yttrium or a rare earth oxide. Catalyst compositions are disclosedherein. Processes disclosed herein include processes for theoligomerization of light olefin containing feeds comprising contactingone or more olefins with the disclosed catalyst and the subsequenthydroformylation or hydrogenation of the higher olefin to producealcohols or saturated hydrocarbons. All numerical values within thedetailed description and the claims herein are understood as modified by“about.”

In step one of an improved oligomerization catalyst preparation, a10-ring zeolite is treated with an yttrium or rare earth salt solutionfollowed by air calcinations to convert at least some of the surfaceacid sites to yttrium or rare earth oxide bound sites.

The disclosure describes a method for the preparation of a yttrium orrare earth surface modified 10-ring zeolite oligomerization catalystsystem. It describes a process where in step (1) a desired amount of theyttrium or rare earth is reacted as the yttrium or rare earth saltsolution with the 10-ring zeolite to reduce the surface acidity of the10-ring zeolite. Incipient wetness is defined as the condition when justenough liquid has been added to a porous solid to just fill all thepore. If more liquid is added to the mixture, it coats the outersurface, changing the appearance from dull to glistening. On drying,catalyst materials added in an incipient wetness impregnation willdeposit in the pores rather than on the outer surface (see “PetroleumCatalysis in Nontechnical Language”, by John Magee and Geoffrey Dolbear;copyright 1998 by Pennwell Publishing Company, Tulsa, Okla.

Yttrium oxide and lanthanum oxide are exemplary embodiments of thespecific oxides that are useful in this disclosure.

In the second step of the preparative method of the disclosure, theyttria or rare earth bound material formed in step (1) is air dried at100° C., calcined in air at 400° C. to form corresponding oxide, thencooled and available for use as an oligomerization catalyst.

One of the advantages of this preparative method is that there is anoptimum amount of yttrium oxide or rare earth oxide that is reacted withthe 10-ring zeolite surface acid sites such that the most desirableproduct selectivity and reactivity is achieved. Thus, one can controlthe amount of yttrium or rare earth reagent required. Another advantageof the method disclosed is that the catalyst compositions of thispreparative method are thermally stable at temperatures at least toabout 300° C., temperatures well above the end or run temperature forolefin oligomerization to higher olefin products. Another advantage ofthe method disclosed is that the resulting catalyst is useful with bothpropylene and butene feed streams to generate higher olefin products.

The present disclosure also provides for a process for producing ahigher olefin by oligomerizing a lower olefin, the process comprising:contacting the lower olefin under oligomerization conditions with asubstantially surface-deactivated catalyst composition comprising azeolite catalyst having active internal Brönsted acid sites andsubstantially inactive surface acid sites achieved by the presence of arare earth or yttrium oxide on the surface.

Additionally, the present disclosure includes a method of making ahigher olefin from a lower olefin containing stream, the methodcomprising: contacting the olefin containing stream with asurface-deactivated catalyst composition comprising a zeolite catalysthaving active internal Brönsted acid sites and substantially inactivesurface acid sites achieved by the presence of a rare earth or yttriumoxide on the surface, thereby producing a higher olefin stream and alighter olefin or vent stream; separating the lighter olefin or ventstream from the higher olefin stream; and contacting a portion of theseparated lighter or vent stream with the surface-deactivated catalystcomposition. The method further comprising contacting at least a portionof the higher olefin stream with a catalyst for hydroformylation.

The method of making a substantially surface-deactivated catalystcomposition optionally includes: contacting a zeolite catalyst with arare earth or yttrium salt solution, followed by air calcination toconvert the surface species into the corresponding oxide, and thereforerendering the surface of the zeolite catalyst substantially inactive foracidic reaction. Rare earth or yttrium oxides are solids and cannot beintroduced as such. Accordingly, they are introduced as soluble saltsolutions (incipient wetness method), then converted to oxides.

This catalyst composition is useful for the preparation of olefinderivatives via olefin oligomerization to produce lightly branchedhigher olefins. Such lightly branched higher olefins are formed by themethod comprising the steps of: (1) treating a zeolite (e.g., a 10-ringzeolite) via incipient wetness with a yttrium or rare earth saltsolution, (2) drying the impregnated zeolite catalyst overnight in airat temperature in the range between about 100 to 120° C., preferably100° C., and (3) beating the impregnated zeolite catalyst in the rangebetween about 350 to 450° C., preferably 400° C., in air for four hoursso the yttrium or rare earth is converted to the corresponding oxide,and cooling the catalyst.

The zeolite is chosen from ZSM-22, ZSM-23, or ZSM-57.

The rare earth oxide used to modify the zeolite surface acid sites ischosen from lanthanum oxide or lanthanide oxides.

Furthermore, the present disclosure includes a method for thepreparation of lightly branched higher olefins (e.g., between about C₆to about C₁₅ range) via olefin oligomerization comprises contacting a C₃⁼ to C₅ ⁼ light olefin containing stream using a modified 10-ringzeolite catalyst where the surface acid sites are at least partlyneutralized with yttrium or rare earth oxides.

The reaction of the yttrium or rare earth modified 10-ring zeolitecatalyst with the olefin containing stream is conducted at a temperaturein the range between about 150 to about 250° C. The reaction of theolefin containing stream with the catalyst is carried at a pressurebetween about 300 to about 1000 psig and a feed flow rate between about0.1 to about 10 WHSV.

The olefin in the olefin containing stream is chosen from propylene,butenes including 1- and 2-butene (cis and trans), isobutylene, orpentenes including 1- and 2-pentene (cis and trans), 2-methyl-2-buteneor 3-methyl-1-butene.

Sources of the olefin in the olefin containing stream are from a steamcracker stream or from a C₄ ⁺ fraction separated from the hydrocarbonproduct produced by an oxygenate to olefin reaction unit. C₄ hydrocarbonmixtures are generally available in any refinery employing steamcracking to produce olefins; a crude steam cracked butene stream,Raffinate-1 (the product of remaining after solvent extraction orhydrogenation to remove butadiene from the crude steam cracked butenestream) and Raffinate-2 (the product remaining after removal ofbutadiene and isobutene from the crude steam cracked butene stream).Generally, these streams have compositions within the weight rangesindicated in Table A below.

TABLE A Crude Raffinate 1 Raffinate 2 C₄ Solvent Hydro- Solvent Hydro-Component stream Extraction genation Extraction genation Butadiene30-85%  0-2% 0-2% 0-1% 0-1% C4 0-15%   0-0.5%   0-0.5%   0-0.5%   0-0.5%acetylenes Butene-1 1-30% 20-50% 50-95% 25-75% 75-95% Butene-2 1-15%10-30%  0-20% 15-40%  0-20% Isobutene 0-30%  0-55%  0-35% 0-5% 0-5%N-butane 0-10%  0-55%  0-10%  0-55%  0-10% Iso-butane 0-1%  0-1% 0-1%0-2% 0-2%

Other refinery mixed C₄ streams, such as those obtained by catalyticcracking of naphthas and other refinery feedstocks, typically have thefollowing composition:

Propylene 0-2 wt % Propane 0-2 wt % Butadiene 0-5 wt % Butene-1 5-20 wt% Butene-2 10-50 wt % Isobutene 5-25 wt % Iso-butane 10-45 wt % N-butane5-25 wt %

C₄ hydrocarbon fractions obtained from the conversion of oxygenates,such as methanol, to lower olefins more typically have the followingcomposition:

Propylene 0-1 wt % Propane 0-0.5 wt % Butadiene 0-1 wt % Butene-1 10-40wt % Butene-2 50-85 wt % Isobutene 0-10 wt % N- + iso-butane 0-10 wt %

Any one or any mixture of the above C₄ hydrocarbon mixtures can be usedin the process of the invention. In addition to linear butenes andbutanes, these mixtures typically contain components, such as isobuteneand butadiene, which can be deleterious to the process of the invention.For example, the normal alkylation products of isobutene with benzeneare tert-butylbenzene and iso-butylbenzene which, as previously stated,act as inhibitors to the subsequent oxidation step. Thus, prior to thealkylation step, these mixtures preferably are subjected to butadieneremoval and isobutene removal. For example, isobutene can be removed byselective dimerization or reaction with methanol to produce MTBE,whereas butadiene can be removed by extraction or selectivehydrogenation to butene-1.

In addition to other hydrocarbon components, commercial C₄ hydrocarbonmixtures typically contain other impurities which could be detrimentalto the alkylation process. For example, refinery C₄ hydrocarbon streamstypically contain nitrogen and sulfur impurities, whereas C₄ hydrocarbonstreams obtained by oxygenate conversion process typically containunreacted oxygenates and water. Thus, prior to the alkylation step,these mixtures may also be subjected to one or more of sulfur removal,nitrogen removal and oxygenate removal, in addition to butadiene removaland isobutene removal. Removal of sulfur, nitrogen, oxygenate impuritiesis conveniently effected by one or a combination of caustic treatment,water washing, distillation, adsorption using molecular sieves and/ormembrane separation. Water is also typically removed by adsorption.

Although not preferred, it is also possible to employ a mixture of a C₄alkylating agent, as described above, and C₃ alkylating agent, such aspropylene, as the alkylating agent in the alkylation step of theinvention so that the alkylation step produces a mixture of cumene andsec-butylbenzene. The resultant mixture can then be processed throughoxidation and cleavage, to make a mixture of acetone and MEK, along withphenol, preferably where the molar ratio of acetone to phenol is 0.5:1,to match the demand of bisphenol-A production.

A still further method of making higher olefins from light olefincontaining stream includes contacting the light olefin containing streamwith an oligomerization catalyst comprising a yttrium or rare earthmodified 10-ring zeolite catalyst composition to produce a productcontaining higher olefin and a vent stream; separating the vent streamfrom the higher olefin; and contacting a portion of the separated ventstream with the oligomerization catalyst.

In another embodiment the present disclosure relates to a higher olefinproduct derived from a C₄ ⁺ feed stream, the product characterized byhaving a low extent of branching.

A higher olefin C₈ and C₁₂ product composition having a productbranching defined as: Branching=0×% linear+1×% mono-branched+2×%di-branched+3×% tri-branched, where: % linear+% mono-branched+%di-branched+% tri-branched=100%.

A higher olefin C₁₆ product composition having a product branchingdefined as: Branching=0×% linear+1×% mono-branched+2.5×% (di- andtri-branched) where: % linear+% mono-branched+% (di- andtri-branched)=100%.

In another embodiment the present disclosure relates to a higher olefinproduct derived from a propylene containing feed stream, the productcharacterized by having a low extent of branching.

A higher olefin C₆ product composition having a product branchingdefined as: Branching=0×% linear+1×mono-branched+2×% di-branched, where:% linear+% mono-branched+% di-branched=100%.

A higher olefin C₉ and C₁₂ product composition having a productbranching defined as: Branching=0×% linear+1×% mono-branched+2×%di-branched+3×% tri-branched, where: % linear+% mono-branched+%di-branched+% tri-branched=100%.

In another embodiment of the disclosure, the olefin derivatives from thecatalytic olefin oligomerization process are further converted viahydroformylation and hydrogenation to branched alcohols. The branchedalcohols are usefully esterified with, for example, phthalic anhydride,adipic acid, or trimellitic anhydride to generate esters useful asplasticizers.

In another embodiment of the disclosure, the higher olefin products fromthe catalytic olefin oligomerization process are further converted viahydrogenation to branched saturated hydrocarbons. The branched saturatedhydrocarbons are usefully applied as functional fluids. Furthermore,these higher olefins can be further converted via alkylation withbenzene or phenol to make sulfonate detergent precursors.

The following examples illustrate the present disclosure and theadvantages thereto without limiting the scope thereof.

EXAMPLES Experimental Details

Below are examples of the preparation of comparative catalysts usingcollidine as the surface modifying agent (Comparative Example 1) and ofthe catalyst systems of this disclosure. Other species within the rangeof the detailed description of the disclosure may work.

Comparative Example 1 Preparation of Collidine/ZSM-22

The ZSM-22 catalyst is a ⅛″ trilobe extrudate with 75% zeolite and 25%alumina binder. This zeolite crystal has a SiO₂/Al₂O₃ molar ratio of 65.This is the base case catalyst used for surface modification. See U.S.Pat. Nos. 4,481,177, 4,556,477, and 4902406 assigned to Mobil ChemicalCompany, which are incorporated herein in their entirety by referencethereto.

8.5 g of ZSM-22 as ⅛″ trilobe extrudates as defined above was used forcollidine treatment. 20 cc of pentane were added to a round-bottom flaskcontaining the catalyst. 10 cc of pentane were added to a jar containing0.077 g of collidine (2,4,6-Trimethylpyridine, 99% purity from Aldrich,CAS# 108-75-8). The collidine solution was added to the flask. The finalmixture was allowed to stand at room temperature for two hours withoccasional shaking. Pentane was removed by purging the flask withnitrogen. The catalyst was dried to a constant weight at roomtemperature under vacuum. The resulting catalyst had a collidine/Al(zeolitic Al) molar ratio of 0.2.

Example 2 Preparation of Yttria/ZSM-22

The same base case ZSM-22 catalyst as described in Comparative Example 1was used for preparation of a yttria-containing catalyst. 0.287 g ofyttrium nitrate hexahydrate (Y(NO₃)₃.6H₂O from Aldrich, CAS #13494-98-9) was dissolved in water to make a solution with a volume of 7cc and this solution was impregnated by incipient wetness onto 10 gramsof ⅛″ trilobe extrudates of alumina-bound ZSM-22. The sample was driedin air at 100° C. overnight and heated in air at 0.5° C./min to 400° C.,held at that temperature for 4 hours, and then cooled to roomtemperature. The finished catalyst, designated as 24151-163 below,contains 0.84 wt % of yttria and has a Y/Al (zeolitic Al) molar ratio of0.2. The amounts of materials used for this preparation are shown inTable 1.

Additional catalyst samples containing different levels of yttria onZSM-22 were prepared using the same procedure described above byadjusting the amount of yttrium nitrate impregnated onto the extrudates.Wettability was maintained at 0.70 cc solution per gram of catalyst.Drying and calcination conditions were the same as with sample24151-163. The amounts of materials used for preparation are also shownin Table 1.

TABLE 1 Variation of Y2O3 Loading on ZSM-22 Weight of Weight of Wt % ofY/Al Yttrium Nitrate, ZSM-22 Y₂O₃ Molar Ratio Sample # g Extrudates, gon ZSM-22 (zeolitic Al) 24151-162 0.143 10 0.42 0.1 24151-163 0.287 100.84 0.2 24151-173 1.160 20 1.68 0.4 24151-193 1.750 20 2.52 0.6

Example 3 Preparation of Lanthanum Oxide/ZSM-22

Samples similar to those described in Example 2 were prepared but withlanthanum oxide rather than yttrium oxide impregnated onto ZSM-22extrudates. The two compositions shown in Table 2 were prepared in ananalogous way to those shown in Example 2 using lanthanum nitratehexahydrate (La(NO₃)₃.6H₂O from Aldrich, CAS # 10277-43-77) as thelanthanum source and with wettabilities at 0.70 cc/g catalyst. Dryingand calcination conditions were the same as shown in Example 2.

TABLE 2 Lanthanum Oxide on ZSM-22 Weight of Y/Al Weight of ZSM-22 RatioLanthanum Extrudates, (Zeolitic Sample Sample # Nitrate, g g Al) 1.22 wt% La₂O₃ 24151-173-A 0.65 20 0.2 2.44 wt % La₂O₃ 24151-193-A 1.33 20 0.4

Below are examples of the oligomerization process using the catalystsprepared in Comparative Example 1, Example 2, and Example 3 above. Otherspecies within the range of the detailed description of the disclosuremay work.

Example 4 2-Butene Oligomerization with Untreated ZSM-22

Two grams of base case ZSM-22, as ⅛″ trilobe extrudate with 25% aluminabinder, was used for oligomerization. The catalyst was diluted with sandto 18 cc and charged to an isothermal, down-flow, 0.5″ inch (insidediameter) fixed-bed reactor. The catalyst was dried at 150° C. andatmospheric pressure with 100 cc/min flowing N₂ for 2 hours. N₂ wasturned off and the reactor pressure was set to 750 psig by a groveloader. The 2-butene feed (57.1% cis-butene, 37.8% trans-butene, 2.5%n-butane, 0.8% isobutene and 1-butene, 1.8% others) was introduced intothe reactor at 60 cc/hr for 2 hour, then reduced to 1.7 WHSV while thereactor pressure was increased to 750 psig. After reaching 750 psig, thereactor temperature was ramped at 2° C./min to 200° C. After line outfor 12 hours at 200° C., 750 psig, and 1.7 WHSV on 2-butene feed, liquidproducts were collected in a cold trap. Additional samples werecollected at 2.2 WHSV on 2-butene feed. Representative data are shown inTable 3.

Product carbon number distribution was determined with an HP-5890 GCequipped with a 60 meter DB-1 column (0.25 mm id and 1 μm filmthickness). Product branching was determined with an H₂-GC. This was anHP-5890 GC equipped with (a) a 100 meter DB-1 column (0.25 mm id and 0.5μm film thickness); (b) hydrogen as the carrier gas; and (c) 0.1 g of0.5% Pt/alumina catalyst in the GC insert for in-situ hydrogenation.Both GC used the same temperature program: 2 min at −20° C., 8° C./minto 275° C., hold at 275° C. for 35 min. Branching values were determinedby the following formulas:

For C₈ and C₁₂ olefins:

Branching=0×% linear+1×% mono-branched+2×di-branched+3×% tri-branched

-   -   Where: % linear+% mono-branched+% di-branched+%        tri-branched=100%

For C₁₆ olefins:

Branching=0×% linear+1×% mono-branched+2.5×% (di- and tri-branched)

-   -   Where: % linear+% mono-branched+% (di- and tri-branched)=100%

An average branching index of 2.5 was used for di- and tri-branched C₁₆species since these components overlapped on our H₂-GC. Representativedata are tabulated below.

Comparative Example 5 2-Butene Oligomerization with Collidine/ZSM-22

Eight grams of collidine-treated ZSM-22, as prepared in ComparativeExample 1, was used for oligomerization. The catalyst was diluted withsand to 18 cc and charged to an isothermal, down-flow, 0.5 inch (insidediameter) fixed-bed reactor. The catalyst was dried at 150° C. andatmospheric pressure with 100 cc/min flowing N₂ for 2 hours. N₂ wasturned off and reactor pressure was set to 750 prig by a grove loader.The 2-butene feed (57.1% cis-butene, 37.8% trans-butene, 2.5% n-butane,0.8% isobutene and 1-butene, 1.8% others) was introduced into thereactor at 60 cc/hr for 2 hours, then reduced to 0.18 WHSV (2.3 cc/hr)while the reactor pressure was increased to 750 psig, After reaching 750psig, the reactor temperature was ramped at 2° C./min to 200° C. Afterline out for 12 hours at 200° C., 750 psig, and 0.18 WHSV on 2-butenefeed, liquid products were collected in a cold trap. Representative dataare shown in Table 3.

Data in Table 3 show that collidine-treated ZSM-22 is effective forreducing branching of olefin products while maintaining octeneselectivity. The loss of catalyst activity after surface treatment, asreflected by the reduced feed flow rate to achieve constant conversion,indicates that surface acid sites were titrated by collidine.

However, when the catalyst was tested at elevated temperatures (up to260° C.), a loss of collidine was observed. The loss was evident at 260°C., which resulted in an increase in catalyst activity and productbranching. Representative data are shown in Table 4b.

TABLE 3 2-Butene Oligomerization with ZSM-22 and Collidine-TreatedZSM-22 ZSM-22 ZSM-22 Catalyst Untreated with Collidine Base/Al MolarRatio — 0.2 collidine/Al Sample Identification 508A096005 508A087005Temperature, ° C. 199 200 Pressure, psig 760 747 Feed Flow Rate, WHSV2.2 0.25 Days on Stream 6.7 4.8 Conversion % 57.6 54.7 Selectivity, wt %C4− 0.00 0.00 C5-7 0.48 0.54 C8 = 75.74 76.80 C9-11 0.22 0.21 C12 =15.40 20.27 C16 = 5.84 1.84 C20 = 1.91 0.27 C24+ 0.40 0.08 Sum 100.0100.0 Product Branching Me/C8 1.41 0.97 Me/C12 2.05 1.13 Me/C16 2.281.77

Example 6 2-Butene Oligomerization with Yttria/ZSM-22

Eight grams of ZSM-22, containing 1.68 wt % of yttria (Sample #24151-173) as prepared in Example 2, was used for oligomerization. Thesame procedure described in Example 5 was used to start up the run. Thecatalyst was tested under a variety of process conditions as shown inFIG. 1 (arrows indicate sequence of conditions for data collection).After testing at 250° C. and 300° C., the catalyst performance wasre-evaluated at startup conditions (200° C., 0.18-0.2 WHSV or SV),respectively (FIG. 1).

Representative data are compared with that of untreated ZSM-22 in Table4a. The data show that yttria-containing ZSM-22 is effective forreducing branching of olefin products while maintaining octeneselectivity. The loss of catalyst activity after surface treatment, asreflected by the reduced feed flow rate to achieve constant conversion,indicates that at least some of the surface acid sites were titrated byyttria. The data also show that yttria-containing ZSM-22 can be operatedat 200-300° C. to produce higher olefins with reduced branching.

TABLE 4a 2-Butene Oligomerization with ZSM-22 and Yttria-Treated ZSM-22Catalyst ZSM-22 ZSM-22 ZSM-22 untreated with collidine with 1.68 wt %Y₂O₃ Base/Al Molar Ratio — 0.2 collidine/Al 0.4 Y/Al 0.4 Y/Al 0.4 Y/AlRun Identification 508A096005 508A087014 508B091005 508B091011508B091019 Temperature, ° C. 199 200 200 250 300 Pressure, psig 760 738747 759 753 Feed Flow Rate, WHSV 2.2 0.18 0.18 1.4 10.0 Days on Stream6.7 15.8 4.8 16.3 23.9 Conversion % 57.6 65.2 66.3 86.7 72.3Selectivity, wt % C4− 0.00 0.01 1.27 4.96 3.59 C5-7 0.48 0.61 0.54 1.112.57 C8 = 75.74 71.76 69.50 63.60 66.27 C9-11 0.22 0.23 0.21 0.71 1.39C12 = 15.40 23.44 16.97 19.39 19.31 C16 = 5.84 2.93 8.23 7.88 5.73 C20 =1.91 0.94 3.22 2.30 1.10 C24+ 0.40 0.08 0.06 0.04 0.00 Sum 100.0 100.00100.0 100.0 100.0 Product Branching Me/C8 1.41 1.02 1.14 1.24 1.24Me/C12 2.05 1.22 1.76 1.79 1.87 Me/C16 2.28 1.89 2.25 2.08 2.07

Representative data of yttria/ZSM-22 are also compared with that ofcollidine/ZSM-22 in Table 4b. After a high temperature data collection(260° C. with collidine/ZSM-22 and 300° C. with yttria/ZSM-22), C₈branching (Me/C8) for both catalysts experienced an increase. However,the branching increase for yttria/ZSM-22 catalyst with a deltatemperature of 100° C. is comparable with that of collidine/ZSM-22 witha delta temperature of 60° C., indicating the more stable nature ofyttria/ZSM-22 to elevated temperatures.

TABLE 4b 2-Butene Oligomerization with Collidine/ZSM-22 andYttria/ZSM-22 Catalyst Collidine/ZSM-22 1.68 wt % Y₂O₃/ZSM-22 Base/AlMolar Ratio 0.2 Collidine/Al 0.4 Y/Al Run Identification 508A087014508A087022 508A087024 508B091005 508B091019 508B091023 Temperature, ° C.200 260 200 200 300 200 Pressure, psig 738 755 746 747 753 751 Feed FlowRate, WHSV 0.18 3.1 0.19 0.18 10.0 0.19 Days on Stream 15.8 20.2 23.84.8 23.9 26.8 Conversion % 65.2 78.3 86.1 66.3 72.3 91.4 Selectivity, wt% C4− 0.01 1.21 0.00 1.27 3.59 2.81 C5-7 0.61 1.39 0.60 0.54 2.57 0.64C8 = 71.76 63.68 59.68 69.50 66.27 52.04 C9-11 0.23 0.85 0.30 0.21 1.390.48 C12 = 23.44 25.46 30.79 16.97 19.31 26.40 C16 = 2.93 5.28 5.89 8.235.73 12.82 C20 = 0.94 1.60 2.34 3.22 1.10 4.70 C24+ 0.08 0.52 0.41 0.060.00 0.10 Sum 100.0 100.0 100.0 100.0 100.0 100.0 Product BranchingMe/C8 1.02 1.15 1.19 1.14 1.24 1.29 Me/C12 1.22 1.48 1.43 1.76 1.87 1.96Me/C16 1.89 1.97 2.05 2.25 2.07 2.15

Catalysts with 0.42, 0.84 and 2.52 wt % yttria, as prepared in Example2, were also tested for 2-butene oligomerization. It was found that the0.42% and 0.84% yttria samples did not have sufficient levels of yttriaon catalysts surface to reduce product branching. The 2.52% yttriasample, on the other hand, had a little too much yttria on the catalyst.The excess yttria did not perform as well as the 1.68 wt % yttriasample.

Example 7 2-Butene Oligomerization with Lanthanum Oxide/ZSM-22

Eight grams of ZSM-22, containing 2.44 wt % of La₂O₃ as prepared inExample 3, was used for oligomerization. The same procedure described inExample 5 was used to start up the run. The catalyst was tested at 200°C. Representative data are compared with that of ZSM-22,collidine-treated ZSM-22, yttria-treated ZSM-22 in Table 5. The datashow that La₂O₃-containing ZSM-22 is effective for reducing branching ofolefin products while maintaining octene selectivity. The loss ofcatalyst activity after surface treatment, as reflected by the reducedfeed flow rate to achieve constant conversion, indicates that at leastsome of the surface acid sites were titrated by La₂O₃.

TABLE 5 Comparison of Catalyst Performance for 2-Butene OligomerizationZSM-22 ZSM-22 ZSM-22 ZSM-22 Catalyst Untreated with collidine with 1.68%Y₂O₃ with 2.44% La₂O₃ Base/Al Molar Ratio — 0.2 0.4 Y/Al 0.4 La/Alcollidine/Al Run Identification 508A096005 508A087014 508A091004508A098011 Temperature, ° C. 199 200 200 200 Pressure, psig 760 738 725776 Feed Flow Rate, WHSV 2.2 0.18 0.17 0.18 Days on Stream 6.7 15.8 3.820.8 Conversion % 57.6 65.2 66.3 55.01 Selectivity, wt % C4− 0.00 0.010.84 0.00 C5-7 0.48 0.61 0.70 0.56 C8 = 75.74 71.76 72.10 75.57 C9-110.22 0.23 0.27 0.48 C12 = 15.40 23.44 16.74 16.18 C16 = 5.84 2.93 7.476.22 C20 = 1.91 0.94 1.85 0.99 C24+ 0.40 0.08 0.03 0.00 Sum 100.0 100.0100.0 100.0 Product Branching Me/C8 1.41 1.02 1.15 1.16 Me/C12 2.05 1.221.74 1.72 Me/C16 2.28 1.89 2.21 2.11

Example 8 Propylene Oligomerization with ZSM-22

0.5 gram of base case ZSM-22 was used for propylene oligomerization. Asimilar startup procedure described in Example 5 was used to start therun using propylene feed (99% purity) as feed. The catalyst was testedat 200° C. Representative data are shown in Table 6. Branching valueswere determined by the following formulas.

For C₆ olefins:

Branching=0×% linear+1×% mono-branched+2×% di-branched

-   -   Where: % linear+% mono-branched+% di-branched=100%

For C₉ and C₁₂ olefins:

Branching=0×% linear+1×% mono-branched+2×% di-branched+3×% tri-branched

-   -   Where: % linear+% mono-branched+% di-branched+%        tri-branched=100%

Example 9 Propylene Oligomerization with Yttria/ZSM-22

1.4 grams of ZSM-22, containing 0.84 wt % of Y₂O₃ as prepared in Example2, were used for propylene oligomerization. A similar startup proceduredescribed in Example 5 was used to start the run using propylene (99%purity) as feed. The catalyst was tested at 200° C. Representative dataare shown in Table 6.

Tests were also conducted using ZSM-22 modified with three differentlevels of yttria, as prepared in Example 2 (0.42 wt % Y₂O₃, sample24151-162; 1.68 wt % Y₂O₃, sample 24151-173; and 2.52 wt % Y₂O₃, sample24151-193). The catalyst was tested at 200° C. Representative data areshown in Table 6.

Example 10 Propylene Oligomerization with Lanthanum Oxide/ZSM-22

Tests were also conducted using ZSM-22 modified with two differentlevels of lanthanum oxide, as prepared in Example 3. A similar startupprocedure described in Example 5 was used to start the run usingpropylene (99% purity) as feed. The 1.22 wt % La₂O₃ sample was tested at200° C. The 2.44 wt % La₂O₃ sample was tested at 230° C. due to itsreduced activity. Representative data are also shown in Table 6.

The results in Table 6 show that ZSM-22 catalysts modified with yttriaor lanthanum oxide are effective for reducing branching of the C₉ andC₁₂ higher olefin products. The loss of catalyst activity after surfacetreatment, as reflected by the reduced feed flow rate to achieve similarconversion, indicates that at least some of the surface acid sites weretitrated by yttria or lanthanum oxide.

TABLE 6 Comparison of Propylene Oligomerization Data 0.42 wt % 0.84 wt %1.68 wt % 2.52 wt % 1.22 wt % 2.44 wt % ZSM-22 Catalyst Untreated Y₂O₃Y₂O₃ Y₂O₃ Y₂O₃ La₂O₃ La₂O₃ Y/Al or La/Al Molar 0.1 0.2 0.4 0.6 0.2 0.4Ratio Sample # — 24151- 24151-163 24151- 24151- 24151-173-A 24151-193-A162 173 193 Run Identification 512A011-13 512A027-2 512A022-3 512A024-2512A026-1 512A025-5 512A033-10 Temperature, ° C. 200 201 200 200 201 200230 Pressure, psig 760 751 754 748 752 756 753 Feed Flow Rate, 8.0 2.81.6 1.6 1.7 1.6 13 WHSV Days on Stream 7.9 1.8 2.8 1.8 0.8 4.8 6.8Conversion % 91.3 82.34 87.2 88.4 71.3 81.8 92.93 Selectivity, wt % C30.19 0.00 0.00 0.00 0.00 0.00 0.00 C4 = s 0.04 0.05 0.04 0.05 0.03 0.050.10 C4 0.02 0.01 0.04 0.02 0.02 0.04 0.02 C5s 1.88 0.16 0.23 0.28 0.250.19 0.31 C6 46.03 62.99 58.86 51.06 60.50 62.77 56.75 C7-8 0.56 0.320.41 0.63 0.50 0.42 0.57 C9 34.19 23.64 24.72 27.12 22.69 22.78 27.09C10-11 0.57 0.23 0.29 0.62 0.22 0.31 0.47 C12 14.90 10.72 12.71 16.1312.73 11.34 12.03 C15 1.27 1.47 2.25 2.92 2.53 1.75 2.11 C16+ 0.35 0.410.42 1.16 0.52 0.32 0.55 Sum 100.0 100.0 100.0 100.0 100.0 100.0 100.0Product Branching Me/C6 0.93 0.92 0.92 0.92 0.91 0.92 0.90 Me/C9 1.851.63 1.58 1.61 1.62 1.56 1.49 Me/C12 2.42 2.32 2.30 2.32 2.32 2.30 2.17

The examples above show that rare earth and yttrium oxides can be usedto modify surface acid sites of 10-ring zeolites such as ZSM-22. Whenused for olefin oligomerization, the modified catalysts are effectivefor reducing product branching. Most importantly, the modified catalystcan be used at 200-300° C. to produce higher olefins. Therefore, thesecatalysts should survive commercial end of cycle temperature of about250° C. Unlike collidine which decomposes during air regeneration, rareearth and yttrium oxides are stable and should survive oxidativecatalyst regeneration.

Applicants have attempted to disclose all embodiments and applicationsof the disclosed subject matter that could be reasonably foreseen.However, there may be unforeseeable, insubstantial modifications thatremain as equivalents. While the present disclosure has been describedin conjunction with specific, exemplary embodiments thereof, it isevident that many alternations, modifications, and variations will beapparent to those skilled in the art in light of the foregoingdescription without departing from the spirit or scope of the presentdisclosure. Accordingly, the present disclosure is intended to embraceall such alterations, modifications, and variations of the abovedetailed description. All patents and other documents cited herein,including priority documents, are fully incorporated by reference to theextent such disclosure is not inconsistent with this disclosure and forall jurisdictions in which such incorporation is permitted. Whennumerical lower limits and numerical upper limits are listed herein,ranges from any lower limit to any upper limit are contemplated.

1. A surface-deactivated catalyst composition comprising a zeolitecatalyst having active internal Brönsted acid sites and containing asurface-deactivating amount of a rare earth or yttrium oxide, andwherein the amount ranges from greater than 0.84 wt. % to less than 2.52wt. %.
 2. The catalyst composition according to claim 1, wherein saidcatalyst composition is stable at least to 300° C.
 3. The catalystcomposition according to claim 1, wherein said zeolite catalyst ischosen from ZSM-22, ZSM-23, or ZSM-57.
 4. The catalyst compositionaccording to claim 1, wherein said rare earth oxide is chosen fromlanthanum oxide or lanthanides oxide.
 5. The catalyst compositionaccording to claim 1, wherein said zeolite catalyst is a 10-ringzeolite. 6-17. (canceled)
 18. A method of making a surface-deactivatedcatalyst composition comprising: a zeolite catalyst with asurface-deactivating amount of a rare earth or yttrium oxide forrendering the surface of said zeolite catalyst substantially inactivefor acidic reaction, and wherein the amount ranges from greater than0.84 wt. % to less than 2.52 wt. %.
 19. The method according to claim18, wherein said substantially surface-deactivated catalyst compositionis stable at least to 300° C.
 20. The method according to claim 18,wherein said zeolite catalyst is chosen from ZSM-22, ZSM-23, or ZSM-57.21. The method according to claim 18, wherein said rare earth oxide ischosen from lanthanum oxide or lanthanides oxide.
 22. The methodaccording to claim 20, wherein said zeolite catalyst is a 10-ringzeolite.